This invention relates to an electric shutter control device of a camera. As is commonly known, in order to electrically control the mechanical closing time of the sector by means of an electromagnet or the like in an electric shutter, it is necessary to turn on and off the control circuit for said electromagnet in accurate synchronization with the opening and closing opertion of the sector. In this case it is essential to suitably select the time duration from the time when the electric circuit starts operating until the sector has been opened (sector advancing time) and the time duration from the time when a reversing signal is developed from the control circuit until the sector has been closed (electromagnet delay time). The sector advancing time is generally longer than the electromagnet delay time and therefore it is necessary that the control time determined by the control circuit is selected to be longer than the exposure time to be realized. Moreover, these times vary for different shutters due to the nonuniformity of the mechanical inertia and the holding force of the electromagnet umployed.
To solve the above-mentioned problem, a method has been proposed heretofore to serially connect an adjustable resistor to the timing circuit and thereby correct the control time by always adding a constant time corresponding to the difference between the sector advancing time and the electromagnet delay time to said control time. This method can be used when exposure factor informations, such as diaphragm aperture, are introduced through a diaphragm or filter disposed in front of the light receiving portion, but not when the exposure factor informations are introduced by means of resistors which vary the switching level of the switching circuit. This is because the time to be corrected varies with the variation of the switching level.
In view of the foregoing, according to one embodiment of this invention an exposure time adjusting circuit composed of a serial connection of a diode and an varies resistor is connected in parallel to the electromagnet used for controlling the sector closing operation to thereby control the electromagnet delay time until it becomes equal to the sector advancing time. According to another embodiment of this invention a delay circuit composed of a transistor, a capacitor and adjustable resistors is arranged between the output terminal of the switching circuit and the electromagnet to thereby control the electromagnet delay time until it becomes equal to the sector advancing time. With such arrangements it is possible to match the exposure time with the control circuit irrespective of what method is employed for introducing the exposure factor informations, such as diaphragm aperture, etc. The circuit of this invention is applicable especially when a shutter is arranged in the exchangeable objective and the control circuit is accomodated within the camera body, because the circuit of this invention can compensate the nonuniformity of time adjusted by different shutters.